Add plotting script as a post processing tool

It would be useful to have a plotting script that reads the information of a .json file (dataset, x title, x limits, y title ,y limits, ...) and plots the distribution's as written on the .json file, with the CMS labels, and other necessary information.

• Implement arbitrary number of weight systematics and variable-based systematics for bands in the plots
• Implement parallelisation with htcondor for quick scale out
• Implement CMS label and lumi string in JSON
• Include an option for splitting eta regions: inclusive, EB-EB, EB-EE, EE-EB, EE-EE, not EB-EB